Enhanced degradation of organic dye in aqueous solutions by bicarbonate-activated hydrogen peroxide with a rosin-based copper catalyst

Developing novel, efficient, and low-cost degradable catalysts for catalytic organic dyes oxidative-degradation has received increasing attention in recent years. Herein, a novel β-CD grafted rosin polymer (RP-g-CD) was successfully synthesized, and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), specific surface area and pore size analyzer (BET), and X-ray photoelectron spectroscopy (XPS). Using RP-g-CD as a supported copper (II) (Cu2+) catalyst, the oxidative degradation of methylene blue (MB) in aqueous solutions was performed by using bicarbonate-activated hydrogen peroxide (BAP) system. The as-synthesized Cu2+/RP-g-CD catalyst exhibited excellent catalytic oxidation performance towards MB with over 99 % removal efficiency in 30 min and high reaction rate constant of 0.0134 min−1. In weakly alkaline solutions, the Cu2+ leaching from the Cu2+/RP-g-CD catalyst is efficiently prevented and the MB removal efficiency remained up to 92 % in catalytic activity in the 4-cycle catalytic experiments. The degradation experiments indicated that the introduction of β-CD in RP-g-CD could promote the rapid capture of MB by the formation of host-guest inclusion complexes. Meanwhile, the loaded Cu2+ could also catalyze the degradation of MB, further improving the removal efficiency in BAP system. The catalytic oxidation mechanism for the MB degradation was investigated systematically via liquid chromatography-mass spectrometry (LC-MS). The results of electron spin resonance (ESR) analysis also indicated that the hydroxyl radical (•OH) has played crucial roles in the degradation process of MB. Finally, the possible decomposition routes of MB were proposed in this system, providing a feasible technical approach for efficient removal of organic dyes.